Mattress core



FIG. 1 is a perspective view of the mattress core with one mattress element, showing the design thereof.

FIG. 2 is a detailed view of a portion of the mattress core with one mattress element that would be generated by sectioning along lines A-A and B-B.

FIG. 3 is a top plan view of the mattress core with one mattress element.

FIG. 4 is a bottom plan view of the mattress core with one mattress element.

FIG. 5 is an end view of the mattress core with one mattress element.

FIG. 6 is a side view of the mattress core with one mattress element.

FIG. 7 is a side view of the inverted mattress core with one mattress element; and,

FIG. 8 is a side view of the mattress core with two mattress elements sandwiched together, where the mattress element depicted in broken lines forms no part of the claimed design. 

CLAIM The ornamental design for a mattress core, as shown and described. 